Can anyone recommend an inflatable kayak that i can use for touring on rivers/lakes and some sea ?
I dont have the space for a rigid kayak so it'll have to be an inflatable. So far I've only seen those on Decathlon site.

Another vote for Gumotex.https://www.gumotexboats.com/en/inflatable-kayaks We have a two man Safari, which has been replaced by the Twist by the look of it. We have paddled the Trent, Severn, Wye rivers, and the Dart, Camel and the Helford Estuaries with it quite happily. I wouldn't go very far off-shore with it though, like many inflatables it is badly affected by the wind.

The advantage with the Gumotex boats is that they are single skinned. Lots of other boats have air bladders encased in a tarpaulin outer layer. Once water gets between the layers they are a real pain to dry. If you have a puncture, single skinned boats are easier to fix. You don't have to remove an air bladder and, once fixed, try and get it back in again.

No, I don't think that's correct. The two layers are thinner than the single thick layer used in the Gumotex boats. The air bladders in double layered boats are very thin. All the protection has to come from the single layer of tarpaulin.

I've seen a lot of suggestions for Gumotex when people ask about "budget inflatables" such as Decathlons itiwit. I've read there have been issues with the lighter material they use on the Twist. Does anyone know if that's not a problem now? If the twist is easier to puncture it would put me off.

I've got the latest version of The Twist and can confirm it's bomb-proof, despite the material being much lighter than the heavy rubbery stuff used in the previous incarnation. The only problem I had was that the inflatable back and foot rests are a bit Mickey Mouse, so I replaced them with a commercial sit-on-top backrest and made my own design of foot 'stirrups' from webbing - they work fine. Gumotex definitely isn't a bargain brand - you pay a lot, but get a bomb proof boat which packs down far smaller than the competition. (Not to be confused with 'Intex' which IS a budget brand.)